This seems like a good time to experiment with geopolymer cast stone to make the first ever earthbag stone dome. The mountain range near our home is predominantly limestone, so the main material is readily at hand. I recently tracked down a supplier and am in the process of obtaining materials to make some test bags.
The ancients had to make the soil binding materials from scratch using salt, wood ashes, etc. But now the basic ingredients (sodium carbonate and lime) can be purchased off the shelf and mixed with limestone and water. In fact, the process is so simple that I’m surprised more people are not investigating the process.
The end product is actual stone, not just something “hard as rock”. It would be fire and rot proof, bullet resistant (almost bulletproof at some point after it gains hardness), totally waterproof obviously, and could possibly last thousands of years. Not much else can compare to this. Even modern concrete falls way short, because it’s too brittle. Concrete has a lifespan closer to 50-100 years in most cases (I’m talking about lifespans of actual structures, not some theoretical time period). The next closest thing might be Roman concrete that was used to make the Pantheon in Rome, among other structures. More about Roman concrete here.